The present invention relates to a dielectric ceramic composition of a high dielectric constant system, capable of baking in a short time, at a baking temperature of 800.degree. to 1000.degree. C., in the atmosphere, neutral atmosphere or reducing atmosphere.
As materials of high dielectric constant of ceramic capacitors which are progressively reduced in size and enlarged in capacity, materials mainly composed of barium titanate have been hitherto employed. But to sinter these materials, it is required to bake in the atmosphere at a high temperature of about 1300.degree. C. Therefore, when fabricating laminate ceramic capacitors, expensive noble metals such as platinum and palladium are indispensable as the electrode materials, and in particular along with the capacity increasing trend, the internal electrode material pushed up the material cost.
To the contrary, recently, it has been attempted to lower the cost of the laminate ceramic capacitors by, among others, a method of providing barium titanate material with resistance to reduction, and baking in an atmosphere of low oxygen partial pressure by using an inexpensive base metal as electrode material or a method of baking at a low temperature of about 1000.degree. C. by using a silver-palladium alloy electrode material mainly composed of lead dielectric material and inexpensive silver.
On the other hand, in the electronic appliances where reduction of size and enhancement of reliability are demanded, the hybrid IC of high packaging density is promoted, and the demand for thick film capacitor is mounting to replace the conventional chip capacitor. To fabricate this thick film capacitor, a dielectric capable of baking at low temperature and in a short time is requried, and the lead dielectric is used mainly as its material. Therefore, as the material applicable to both increase of capacity of laminate chip capacitor and increase of thickness of capacity, the lead dielectric is being developed intensively.
Incidentally, PbTiO.sub.3 -Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 solid solution and PbZrO.sub.3 -Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 -Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3 solid solution are compositions with high dielectric constnat baked in the atmosphere at 1100.degree. C. or lower temperature as disclosed in the Japanese Patent Laid-Open No. 61-155249 and No. 61-155248, but it is necessary to keep the baking temperature for several hours in order to heighten the dielectric constant and obtain sinters having a sufficiently dense texture. On the other hand, when fabricating a thick film capacitor for hybrid IC, low temperature, short-time baking is indispensable, and these dielectric materials are not sintered completely in such condition, and therefore desired characteristics are not obtained. Still worse, due to heat temperature in neutral or reducing atmosphere for a long time, oxygen defects are likely to occur in the dielectric ceramics, which led to practical problems such as lowering of dielectric constant and reduction of insulation resistance.